This invention relates to beverages such as beer, ale, malt liquor, porter, shandy, and others which are made from or contain fermented extracts of malt, of improved stability against light and their manufacture.
It is well known that beer, ale, malt liquor and other malt beverages and blended beverages containing them as traditionally manufactured are not stable to light. Light of both visible and ultraviolet wave lengths affects the flavor of these products adversely, producing the so-called skunky flavor also referred to as light-struck or sunstruck flavor. It is also well known that the formation of skunky flavor is caused by chemical changes producing mercaptans, such as 3-methyl-2-butene-1-thiol (MBT). Sensory tests show that the olfactory threshold for this compound is only a few parts per billion.
Many efforts have been made in the past to overcome this problem. One of these is to shield the product from the effects of harmful radiation by packaging it in cans or dark amber bottles. Whereas, the cans afford almost complete protection against skunky flavor development, amber bottles provide protection only for several hours when exposed to direct sunlight.
Other types of glass bottles such as those made using olive green and light green glass give significantly less protection whereas in clear glass bottles the product becomes skunky almost instantly when exposed to direct sunlight. The effectiveness of glass generally in protecting the product against formation of skunky flavor depends upon the degree to which the glass is able to prevent the harmful radiation from reaching the product. The light energy needed to produce skunky flavor in beer has been found to be in the region of 1,000-10,000 A (Angstroms) in U.S. Pat. No. 3,044,870. In terms of the degree of effectiveness of glass, dark amber bottles are the best followed by olive green and then light green bottles. Clear bottles provide little or no screening against the harmful effects.
Protection of the beverage in the package does not completely insure it against the formation of skunky flavor. Even short term exposure of the product such as occurs when in-process beer or ale is exposed to cellar lights through sight glass windows or the exposure of the product in the drinking glass to direct sunlight (such as may occur during outdoor picnics and sports events) or to diffuse light at home can and will cause the development of skunky flavor.
It is therefore desirable that the product itself be rendered safe against the action of harmful radiation instead of shielding it by packaging in specific materials. Previous efforts have been described in several patents such as U.S. Pat. Nos. 3,044,879; 3,798,332; 3,558,326 and 3,536,495. Basically the art described in these patents consists of chemically treating hops in such a way as to stabilize the light sensitive branch of the hop bitter acids by catalytic reduction thus preventing its participation in a subsequent reaction with sulfhydryl groups to produce the skunky flavored MBT compound. The process of treating hops is complex, cumbersome, time consuming and obviously expensive.
Furthermore, even beer or other beverages made with hops so treated do not possess unlimited life against the effect of radiation and such hop treatment involves a severe departure from traditional brewing which calls for the use of whole hops in developing the overall taste factors desired.